Serum separating method

ABSTRACT

The separation of a sample of blood into serum and clot portions is accomplished by means of a sealant consisting essentially of a silicone fluid and silica dispersed therein. The separation is accomplished by inserting a device containing a supply of the sealant into a container holding a sample of the blood, the device being characterized by a nozzle portion which extends into the sample. The container and device are centrifuged so that it separates into serum and clot portions and the sealant, having a specific gravity of at least 1.026, separates the two portions.

United States Patent [191 Lukacs et al.

[ Dec. 25, 1973 SERUM SEPARATING METHOD Inventors: Michel J. Lukacs,Goshen, N.Y.; [an

H. Jacoby, Franklin Lakes, NJ.

Assignee: Lukacs & Jacoby Associates,

Goshen, NY.

Filed: July 10, 1972 Appl. No.: 270,278

US. Cl 233/1 A, 210/65, 210/83 Int. Cl 801d 21/26 Field of Search106/287 SB; 210/65,

210/83, DIG. 23; 233/1, 26

References Cited UNITED STATES PATENTS 3/1972 Adler ..2l0/83 4/1970Coleman ..2lO/83 Primary Examiner-Samih N. Zahama AssistantExaminer-Robert G. Mukai Attorney.lohn A. Mitchell et al.

ABSTRACT 3 Claims, 8 Drawing Figures PATENTED M825 I975 FIG. 4

FIG. 2 FIG. 3

SERUM SEPARATING METHOD BACKGROUND OF THE INVENTION This inventionrelates to a method, apparatus and composition of matter for separatinga blood sample by centrifuging into clot portions, so that the serum maybe quickly and readily removed without contamination by the clotportion.

In recent years, biomedical and hospital laboratories have been facedwith increasing demands for more and more routine, as well asspecialized, diagnostic tests of blood samples. To meet the demands ofthese tests equipment has been devised which automatically takes asample or specimen of blood which has been placed in a cup and subjectsit to a series of programmed tests which eventuate in a readout on arecord member. While these analyzers have increased the efficiency ofperforming the necessary tests, a problem has continued in finding waysand means of separating the serum from the clot portion and removing theserum for analysis. Various types of tube and plug devices have beensuggested by the prior art. For example, in U.S. Pat. No. 3,512,940,issued May 19, 1970, a device consisting of a tube with a filter at oneend thereof is inserted into a second but larger diameter tubecontaining a sample of the material desired to be filtered. In U.S. Pat.No. 3,508,653, issued Apr. 28, 1970, a piston in the form of a solidplug is driven through a centrifuged blood sample so as to positionitself between the serum and clot portions of the centrifuged sample.The tube within the tube concept of US. Pat. No. 3,512,940 suffers fromthe apparent deficiency of being costly and not readily adaptable fordisposal after a single use. The plug' arrangement of US. Pat. No.3,508,653 has the shortcoming of utilizing a solid plug member whichwhen subjected to a substantial centrifugal force, may also developradial forces acting against the side of the sample tube, thus creatingthe danger of breakage.

SUMMARY OF THE INVENTION a silicone fluid and silica. The sealant has aspecific gravity of at least 1.026 and preferably in the range of 1.030to 1.050. As such, it will normally be at the proper specific gravity todivide the serum and clot portions of the centrifuged sample, sealingthe clot in the container while the serum is removed.

Accordingly, it is an object of the present invention to provide asimple and effective method of obtaining a serum sample duringcentrifuging.

DESCRIPTION OF THE DRAWINGS FIG. 4 is a view similar to FIG. 2 whereinthe blood, the sample tube and dispenser have been subjected to thecomplete centrifuging step;

FIG. 5 is a sectional view of the sample tube with the separator inplace overlying the clot portion with the serum portion removed;

FIG. 6 is an enlarged sectional view of the sealant dispenser showingthe sealant contained therein;

FIG. 7 is a top view of the dispenser of FIG. 6; and

FIG. 8 is a bottom view of the dispenser of FIG. 6.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT Referring to the drawings, acontainer 10 for holding a blood sample is illustrated as a straightside wall sample tube 10 with an open top end 11. Into the open top 11is inserted a dispenser 12. The dispenser 12 has a flange member 14which overlies the top edge 16 of the side wall 18 of the container. Thedispenser 12 includes a body portion 19; consisting of three ringsections 20, 22 and 24. Extending from the body 19 is an elongatednozzle portion 26 and at the end of the nozzle 26 is a tip 28 having anopening 30 therein. The purpose of the three rings 20, 22 and 24 is topermit the dispenser 12 to be used with containers of various diameters.Ring 20 has a shoulder 32 and a side wall 33,-ring 22 a shoulder 34 anda side wall 35, and ring 24 has a shoulder 36 and a side wall 37. Whenusing a narrow container, the dispenser bears on the top edge of theside wall of the container at one of the shoulders 32, 34 or 36 and theside wall of the next smaller ring is parallel with the inner side wallof the container. During centrifuging the relationship between the innersurface of the container and the side wall of the ring insures stabilityof the dispenser during this period.

By utilizing a dispenser as illustrated herein, it is possible to useone dispenser for varying diameter containers.

The body portion 19 of the dispenser has an open end 37 over which isplaced a seal 38. The seal 38 has a small opening 40 therein. The seal38 is not placed over the open end until a sealant 42 has been placed inthe dispenser.

The sealant 42 consists essentially of a silicone fluid with an inertfiller, such as silica, dispersed therein. The sealant should have aspecific gravity of at least 1.026

. and preferably in the range of 1.030 to 1.050.

The normal specific gravity of blood as determined by the pycnometricmethod is considered to be in the range of 1.048 to 1.066 with averagesof 1.052 to 1.063. After centrifuging the specific gravity of the bloodserum which separates from the remainder of the blood is at least 1.026and in the range of 1.026 to 1.031. The specific gravity of the heavierportions such as the erythrocytes is 1.092 to 1.095.

In selecting a sealant it is necessary to select one which has aspecific gravity greater than that of the serum portion. Accordingly,the sealant should have a specific gravity of at least 1.026. However,its specific gravity should not be too high so as to cause it to layersomewhere in the clot portion. Such layering would be of no practicaluse towards obtaining a separated serum portion. A preferred sealantwould have a specific gravity in the range of 1.030 to 1.050.

The sealant is also preferably thioxtropic, water insoluble,substantially non-toxic as well as substantially chemically inert withrespect to the constituents of the blood sample, particularly those inthe serum portion.

A preferred sealant formulation is as follows:

EXAMPLE I Parts by weight The silicone fluid used in Example I was adimethylpolysiloxane polymer made by Union Carbide Corporation andidentified by the designation L- 45. it had a viscosity of 12,500centistokes and a specific gravity of about 0.973 at 25C. The silicawith a specific gravity of 2.65 was an amorphous silica having aparticle size of at least 75 percent being less than 5.0 microns. It wasmade by Whittaker, Clark & Daniels and identified by the designation No.31 Lo Micron". The silica with a specific gravity of 2.3 was ahydrophobic amorphous silica having an average particle size of about 20millimicrons. It was made by Degussa Inc. and identified by thedesignation Aerosil R 972.

The silicone fluid and the silica were mixed together to a thixotropiccondition with a resultant specific gravity of 1.045 to 1.050 to formthe sealant.

The sealant was then placed in a dispenser of the type illustrated inFIG. 6 in particular. The diameter of the flange was 0.70 inches and theoverall length 1.75 inches with the nozzle and tip being 1.10 inches.The opening in the tip was 0.032 inches. The filled dispenser was placedin a standard sample tube having an overall length of 3.875 inches withthe shoulder 32 of the first ring resting on the top of the tube sidewall. The tube had previously been filled with a whole blood specimen towithin 1.10 inches of the open end of the tube. The extent of thedispenser from shoulder 32 to the end of the tip was 1.5 inches. Thus,the dispenser tip and part of the nozzle extended well into the bloodsample.

The tube with the blood sample and dispenser was centrifuged forapproximately 10 minutes. After 5 minutes substantially all of thesealant had passed from the dispenser. The sealant did not disperse butinstead remained homogeneous and settled as a layer between the serumand clot portions of the centrifuged blood. it was noted that thesealant settled as a substantially even layer between the two portionssince its specific gravity of 1.045 to 1.050 was less than that of theclot portion and greater than that of the serum portion. The sealantformed a tight seal against the inner wall of the tube. Also noted wasthe fact, that the sealant had mixed into it, particularly in theportion near the clot portion, fibrant matter which had been filteredout of the serum portion as the sealant settled to its own specificgravity level.

The use of the dispenser which extended into the blood sample expeditedthe procedure since it was not necessary for the sealant to overcome thesurface tension of the blood sample.

With the sealant in place it was possible to merely decant off the serumportion with the clot being trapped behind the sealant.

The specific gravity of the sealant was determined by using a coppersulfate method. The procedure consists of letting drops of the sealantfall into a graded series of solutions of copper sulfate of knownspecific gravity and noting whether the drops rise or fall. The seriesused were graded at 0.005 intervals. Merely by observing the drops itwas possible to determine that the sealant had a specific gravitybetween 1.045 and 1.050.

Another sealant formulation is as follows:

EXAMPLE ll Parts by weight Silicone fluid (dimethylpolysiloxane) I00Silica (specific gravity 1.95) 14 The silicone fluid of Example 11 isthe same dimethylpolysiloxane polymer of Example 1. The silica with aspecific gravity of 1.05 has an average particle size of 16millimicrons. it is made by Henlig & Co. and identified by thedesignation TRI-SlL 404. The specific gravity is from 1.045 to 1.050.

Still another sealant formulation is as follows:

EXAMPLE Ill Parts by weight Silicone fluid (ethyltriethoxysilane) Silica(specific gravity 2.65) 8 Silica (specific gravity 2.3) 20 The siliconefluid of Example 11 is an ethyltriethoxysilane monomer made by UnionCarbide Corporation and identified by the designation A-15. The silicasare the same as those used in Example I.

The filler serves the dual purpose of making the silicone fluidthixotropic and of adjusting the specific gravity to that which isdesired for the resultant sealant. In place of silica other inertfillers which may be used in a fine powdered form are bentoniate,alumina and talc. Others will also occur to those skilled in the art.

Another silicone fluid which may be used is made by Dow CorningCorporation and identified as 200 Fluid.

In selecting silicone fluids and fillers, one should select materialswhich when mixed together will give the desired specific gravity, besubstantially non-toxic, water insoluble and substantially chemicallyinert with respect to the constituents of at least the serum portion.

The dispenser serves to meter out the sealant gradually and this gradualmetering provides sufficient lead time for the centrifugation to takeeffect before the sealant is in place. If the sealant were allowed to bepositioned too soon some unwanted matter, such as red cells or fibrilarlike material, may be trapped in the serum portion by the sealant.

While various examples have been described herein and one embodimentillustrated on the drawings, those skilled in the art may practice theinvention in its various forms by other examples and embodiments withoutdeparting from the scope of the claims herein.

What is claimed is:

1. A method of separating a sample of whole blood into serum and clotportions comprising the steps of:

placing a quantity of whole blood into a container adapted to becentrifuged;

inserting into said container a supply of a thixotropic,

water insoluble, substantially non-toxic sealant consisting essentiallyof a silicone fluid and an inert filler dispersed therein, said sealanthaving a specific gravity in the range of 1.026 to 1.092; and

centrifuging the blood into serum and clot portions until the sealantforms a'separator between said portions.

2. A method as defined in claim 1 wherein the inert filler is silica.

3. A method as defined in claim 1 wherein the sealant has a specificgravity in the range of 1.030 to 1.050.

1. A method of separating a sample of whole blood into serum and clotportions comprising the steps of: placing a quantity of whole blood intoa container adapted to be centrifuged; inserting into said container asupply of a thixotropic, water insoluble, substantially non-toxicsealant consisting essentially of a silicone fluid and an inert fillerdispersed therein, said sealant having a specific gravity in the rangeof 1.026 to 1.092; and centrifuging the blood into serum and clotportions until the sealant forms a separator between said portions.
 2. Amethod as defined in claim 1 wherein the inert filler is silica.
 3. Amethod as defined in claim 1 wherein the sealant has a specific gravityin the range of 1.030 to 1.050.